1. Field of the Invention
The present invention relates to hydro-generators submerged in water converting the hydraulic energy of currents, waves and other the movements into other energy, such as electricity, hydrogen gas, or other energy-bearer. Typically, these units have an energy converter transforming the hydraulic energy into mechanical energy, for example through rotating turbine runner, displacement bodies, foils, buoys, and pneumatic or other devices. The mechanical energy is transmitted through the so-called drive train to the hydro-generator's generator. Typically the drive train and the generator is contained in a bulb housing separating the surrounding water from the gas or air filled internal space housing the drive train, the generator and the auxiliary equipment. The drive train consists of a combination of bearings, shafts, couplings, transmissions, sealing, hydraulic and mechanical components. The generator part of the hydro-generator unit converts the mechanical energy supplied through the drive train into other form of energy, such as electricity, hydrogen or other energy-bearer. The additional auxiliary equipment may provide for removal of leakage water, measurement, control and protective actions.
2. Description of the Prior Art
There is several known design for utilization of the kinetic energy in the free flowing rivers, ocean currents or tidal water movement. Typically, these design ideas address the positioning of the device in relation to the water surface, the bottom or the device's orientation in relation to the current's direction. For example it is known design where a distinctive part of the device act as a flotation chamber. This chamber may contain a fluid, eventually from the surrounding water, with adjustable level to ensure the vertical positioning of the floatation chamber and the attached water turbine in relation to the free water surface. In this case the fluid is not in connection with the energy converter for example air compressor and it's drive train, which is contained, in a completely separated nacelle. It should be noted that the energy transmission via compressed air is far inferior to the electrical system where the rotational movement can be directly introduced into an electric generator while the compressed air transmission contains two additional energy conversion components, the air compressor and the air turbine, which are known to have very poor efficiency. The problems relating to handling of the moving ice covering the free water surface and the introduction of typically humid air into the nacelle containing the air compressor remains unresolved.
The problem with the above and all type of submersed equipment is the prevention of water intrusion from the surrounding into the gas or air filled bulb housing, sometimes called nacelle, in order to protect the drive train, generator and auxiliary equipment from the effect of water and how to the replace the gas or air leaking out from the bulb housing. The prior solutions were based on balancing the pressure of the internal gas or air atmosphere in relation to the surrounding water pressure. This could be achieved by having an automatic control system that pumps the leakage water out from the bulb housing
Typically, the energy needed for the pump action could be generated by the hydro-generator. However, the replacement of the lost gas may be a demanding task. There are three major options: A compressed gas container may be used as a reservoir, a pipeline may carry in the gas from the shore or the gas may be produced inside the unit for example through electrolysis. All these options have some disadvantage. The compressed gas reservoir must be refilled from time to time causing indispensable and costly maintenance operations. The compressed gas line from the shore to the bulb housing might be damaged and in stead of supplying gas, the gas may escape from the bulb housing through the leaking pipe line. The third option, with gas generation inside the bulb housing would surely introduce many additional components and costs or this solution would be primarily reserved for hydro-generator units which has hydrogen and not electricity as main energy product.